The need for economically improving the corrosion resistance of metals is widely recognized in the art. Corrosion is a problem that plagues the common structural metals such as iron, aluminum, magnesium and copper.
Even many exotic structural materials which have a high melting point are difficult to use in high temperature applications. For example, titanium and its alloys corrode rapidly in the atmosphere at elevated temperatures because of nitrification and oxidation. Were it not for this corrosion problem titanium would be an excellent material for applications in rockets, aircraft, nuclear reactors, heating elements, and many other high temperature applications.
It has been recognized that the titanium corrosion problem could be reduced or eliminated by forming a silicide intermetallic compound coating on the exposed surfaces. Titanium forms two silicide intermetallic compounds. The compound Ti.sub.5 Si.sub.3 is a peritectic compound having a melting point of about 2120.degree. C., which is significantly higher than titanium's melting point of 1687.degree. C. The other silicide is Ti Si.sub.2 which has a melting point of 1540.degree. C., somewhat less than that of pure titanium. Both of these intermetallic compounds have excellent corrosion resistance at high temperatures.
Several methods are outlined in U.S. Pat. No. 3,047,419, issued on July 31, 1962, for the formation of silicide coatings on titanium. The patent describes sintering, vapor deposition, flame spray, and cementation techniques for formation of titanium silicide coatings. All of these techniques are somewhat complex and involve the use of high temperatures. It would be highly desirable to form intermetallic compounds in a simple manner.